New optical fiber technologies are continually being developed to accommodate increasing demands for band width and other communication properties. Optical fiber ribbons have been developed to provide increased packing densities, improved accessibility and the like. In the U.S. telecommunications industry, 12-fiber ribbons have become a standard while in Japan, 8-fiber ribbons have commonly been employed. Optical fiber ribbons are disclosed, for example, in the Duecker U.S. Pat. No. 5,881,194, the Lochkovic et al U.S. Pat. No. 5,561,730 and the Hattori et al U.S. Pat. No. 5,524,164, and by McCreary et al, International Wire and Cable Symposium Proceedings (1998):432-439.
Generally, optical fiber ribbons comprise two or more optical fibers embedded and secured within a matrix material. The optical fibers are typically arranged in parallel relation substantially within a single plane. To accommodate increased capacity demands, as many as 24 optical fibers may be arranged in a single linear array in an optical ribbon. In certain applications, it is desirable to separate the optical fiber ribbon into two or more subunits by splitting the optical ribbon. To allow such separation, it has been a common practice to provide the optical fibers which are positioned at the ends of adjacent subunits in side-by-side direct contact with each other, without matrix material therebetween. This arrangement offers a convenient separating mechanism for splitting the optical fiber ribbon into subunits. However, owing to the small size of the individual fibers, their close proximity to one another, and/or the properties of the matrix materials, reliable splitting of the ribbon into subunits has been difficult as uneven tearing or splitting and/or optical fiber damage often results.
Several alternatives have been suggested to provide optical fiber ribbons which may be more reliably split into subunit ribbons. For example, notches have been provided in optical fiber ribbons along the desired tear or split line. In practice, the notches provided a weak area in the ribbon structure and have caused various problems with the handling integrity of the ribbons. Another alternative has been to provide modular subunits in an optical fiber ribbon. In this design, individual subunits are formed by embedding and securing a number of optical fibers in a matrix material. Two or more subunits are then embedded in an encapsulant material to form the optical fiber ribbon containing the modular subunit ribbons. For example, Hattori et al disclose optical fiber ribbon containing two modular subunit ribbons, each of which contains four optical fibers. The subunit ribbons are embedded and secured within an encapsulating material. Similarly, McCreary et al disclose a 24-fiber modular optical fiber ribbon which contains two 12-fiber subunit ribbons. The subunit ribbons are embedded within an encapsulating material to form the 24-fiber optical ribbon.
While the modular type optical fiber ribbon containing subunit ribbons provide improvement over nonmodular optical fiber ribbons in various applications, the modular optical fiber ribbons typically exhibit one or more deficiencies in use. For example, during tearing or splitting of the modular subunits, uneven tear often occurs, resulting in overhang of the encapsulating matrix on one split subunit ribbon and excessive removal of encapsulating material on an adjacent subunit ribbon. The uneven tear or splitting of the encapsulating material can be particularly disadvantageous when the encapsulating material is provided with printed identification information and such information is removed from one of the subunits by uneven tearing. Previous modular optical fiber ribbons have also been known to exhibit delamination of the encapsulating material from the subunits, particularly upon the twisting of the optical fiber ribbons which is conventionally encountered in cabling applications. In yet additional modular optical fiber ribbons, cracking of the encapsulating material has occurred. Accordingly, the need remains for providing improved modular optical fiber ribbons which allow for reliable and even splitting of subunits therefrom and which exhibit improved handling robustness and resist cracking or delamination of the encapsulating material.